I'm the author for mtlx, and admittedly I didn't do anything about efficiency when I implemented it. Is there any initial place I ought to look for tips on inlining? I'll start with the pragmas page (http://www.haskell.org/ghc/docs/7.0.3/html/users_guide/pragmas.html) I suppose. I'm happy for any suggestions--optimizing hasn't been one of my focuses, so it's time for me to learn I suppose! I did switch to newtype definitions in the most recent version (0.1.5), which probably helped a lot compared to data definitions, but there are no inline pragmas in use, so perhaps there are some good opportunities for optimization. ~Mark Snyder
Is the package missing some obvious inlining in the instances?
I just refactored my type and transform system prototype (introduced in [1] but changed since then) from using mtlx [2] (type-indexed monad transformers described in [3]) to mtl using RWST. mtlx allowed me to cleanly separate the various monadic components in a convenient way. Unfortunately, I found it to be too slow. The refactoring was an experiment to see how slow. I was rather surprised:
Running time of a compiled main with a list of tests: ? mtlx (7 transformers): 2 min 52 sec ? mtl (RWST): 0 min 13 sec
It's frustrating to see such a huge performance gap for a better design.
Regards, Sean